Switching power supply no-load detection circuit and detection method

Abstract

The invention relates to a switching power supply no-load detection circuit comprising a sampling circuit, a first counter and a second counter. The clock input ends of the sampling circuit, first counter and second counter are connected to clock input signals, the signal input end of the sampling circuit is connected to switch conducting signals, the signal output end of the sampling circuit is connected to the reset end of the second counter, the signal output end and reset end of the second counter are connected to the reset end of the first counter, and the upper limit value of the second counter is smaller than that of the first counter. The invention further relates to a switching power supply no-load detection method. Thus, analog circuit usage is reduced, whether the switching power supply is unloaded or not is judged by judging whether the switching power supply is loaded or not, structure is simple, integration is facilitated, and the application range is expanded.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a switching power supply, in particular to a no-load detection circuit and a detection method of a switching power supply. Background technique [0002] In electronic devices that use switching power supplies, especially mobile devices, such as mobile power supplies, when the load is removed, the system enters a no-load state and the system enters a standby mode to reduce system power consumption. [0003] see figure 1 As shown, it is the first implementation circuit of no-load detection of switching power supply chip. The traditional no-load detection technology of switching power supply chip is to connect a resistor with small resistance in series on the load path. The voltage drop at the terminal can be used to judge whether the circuit is no-load. [0004] see figure 2 and image 3 As shown, it is the second implementation circuit and its specific implementation of s...

AI Technical Summary

Problems solved by technology

[0005] Disadvantages of the above-mentioned first implementation circuit: because a sampling resistor Rs is added, the value of the resistance needs to be considered comprehensively. If the value is too large, the conversion efficiency will be affected, and the value is small and it is not easy to detect.

[0006] Disadvantages of the above-mentioned second implementation circuit: Although the first implementation circuit has been optimized for the disadvantage of "small value is not easy to detect", it requires complex analog circuit detection, and several threshold voltages need to be set reasonably, such as Vth2 If the setting is too large, the circuit may switch repeatedly between two states (on and off of Q2). If it is too small, it will face the problem that the first realization circuit is not easy to detect.

This scheme also responds to the pseudo-no-load state (short-time current oscillation caused by external disturbances makes the Vds1 voltage lower than the threshold voltage in a certain period), causing the circuit to issue an invalid no-load judgment and switch repeatedly

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